The present disclosure relates to a supply tube for a painting installation, e.g., for the compressed air supply of a turbine in a rotary atomizer or for the supply of an atomizer with a liquid medium such as paint or rinsing agent or for the supply with guide air.
The present disclosure is further directed to a painting robot with a supply tube of this type for the supply of an atomizer guided by the painting robot.
FIG. 1 shows in a simplified form a conventional painting robot 1, which can be used for example in a painting installation for painting motor vehicle body parts. The painting robot 1 has a proximal robot arm 2 and a distal robot arm 3, wherein the proximal robot arm 2 is also designated “Arm 1” according to the pertinent specialist terminology, whereas the distal robot arm 3 is usually designated “Arm 2”. The proximal robot arm 2 is mounted pivotably on a robot base, wherein the robot base can be optionally stationary or moveable and is not shown for the sake of simplicity. The distal robot arm 3, however, is pivotably attached with a swivelling joint 4 to the distal end of the proximal robot arm 2. A multi-element robot wrist 5, which guides a rotary atomizer 6 in a mobile manner is mounted on the end of the distal robot arm 3, wherein the rotary atomizer 6 has as an application element a bell cup 7, which is driven by a turbine 8. The compressed air for driving the turbine 8 is fed through a regulator 9 which is securely installed in the proximal robot arm 2, wherein the regulator 9 regulates the rotary speed of the turbine 8 and thereby also the rotary speed of the bell cup 7 via a corresponding throttling of the introduced air flow. The connection between the regulator 9 and the turbine 8 is guided through the proximal robot arm 2, the swivelling joint 4, the distal robot arm 3 and the robot wrist 5. After a short tube section of a few centimeters with dimensions 9×12 mm the connection downstream from the regulator 9 is divided via a Y-tube 10 into two 9×12 mm-tubes 11, 12, which are then connected by a tube guide element 13 to two reducers 14, 15 in or on the swivelling joint 4. On the downstream side, each of the two reducers 14, 15 is connected to a 6×8 mm tube 16, 17, wherein both 6×8 mm tubes 16, 17 are guided to the turbine 8 through a tube guide element 18, the distal robot arm 3 and the robot wrist 5 and thus drive said turbine 8.
The compressed air supply of the turbine 8 is, therefore, divided into the two 9×12 mm tubes 11, 12 in the proximal robot arm 2 and the two 6×8 mm-tubes 16, 17 in the distal robot arm 3. The large 9×12 mm tubes 11, 12 offer in this case, due to their relatively large internal cross section, the advantage of a correspondingly small flow resistance. However, the large 9×12 mm-tubes 11, 12 are not suitable for installation in the robot wrist 5 as the large 9×12 mm-tubes 11, 12 would not withstand the torsional loads in the robot wrist 5. Therefore, the smaller 6×8 mm-tubes 16, 17 which, due to their smaller cross section, can permanently withstand the torsional loads in the robot wrist 5 during operation, are installed in the robot wrist 5.
In this known painting robot, however, the fact that the flow resistance of the compressed air supply of the turbine 8 is increased between the regulator 9 and the turbine 8 by the relatively small internal cross section of the 6×8 mm tubes 16, 17 is a disadvantage.
For solving this problem, it has been already been envisioned to move the reducer 14, 15 out of the swivelling joint 4 in the direction of flow, i.e. into the distal robot arm 3. This is not achievable, however, due to the torsional loads in the robot wrist 5 and the resulting abrasion of further tubes on the reducers 14, 15. Furthermore, the reducers 14, 15 would not withstand the mechanical loads in the region of the robot wrist 5 if the reducers 14, 15 were moved too close to the robot wrist 5 in the distal robot arm 3. It would not be possible, therefore, to ensure a secure connection between the reducers 14, 15 and the 6×8 mm-tubes 16, 17 in such a solution. In addition, further tubes would also be affected.
Nor can the aforementioned problem be solved by guiding the large 9×12 mm tubes 11, 12 through the robot wrist 5, because such large tubes will not withstand the torsional loads in the robot wrist 5.
Furthermore, in one known approach, e.g., FIG. 4 from DE 603 04 386 T2, a line system with a first supply line and a second supply line is provided, wherein both supply lines obviously have a different internal cross section. This is not, however, a one-piece line but two separate lines with different internal cross sections.
Finally, with regard to the general state of the art, reference is made to the document published by the applicant, “Technical handbook: Introduction to the technique of passenger car painting”. This document, however, discloses only conventional supply tubes and their application in the area of painting technology.
Accordingly, there is a need to reduce the flow resistance in a compressed air supply of a turbine or a guide air supply of a rotary atomizer.